The field of view of the lens of the P4 pro (measured diagonally is 84°.
If you fly to 500 metres, that would cover an area of 750m x 500 m (in 3:2 aspect ratio)
To capture an island measuring 2.7 km x 1.8 km you would have to fly at 1800 metres but the Phantom isn't going to do that and would probably be blown away by high level winds if it could.
You could use a mapping app to fly a grid and capture lots of overlapping images to stitch into an orthophoto like this example I did for a site measuring 1.3 x 0.9 km.
That required two flights and about 400 images
To use a mapping app and stay within the Canadian altitude rules (90 metres), to cover a 2.7 x 1.8km area, you would have to make 14 flights to capture 4700 images with a basic overlap of 65/75%.
The computer horsepower to stitch this would be huge and take a very long time.
If you could fly at 500 metres that would still require 3 flights and about 200 images.
There could be additional complications if the texture of the area is difficult for stitching software (forests or grassland).
Simple answer: you can't easily get a top-down view of 486 hectares (2.7 x 1.8 km).